This invention relates to an apparatus for injecting pressure regulated fuel through fuel injectors into an internal combustion engine.
Fuel injection apparatus have been used to inject pressure regulated fuel into an internal combustion engine through fuel injectors provided in a fuel supply passage extending from a fuel tank. In order to provide a linear relationship between the amount of fuel injected into the engine and the length of time the fuel injector opens, it is required to maintain the pressure differential across the fuel injectors at a predetermined level. For example, Japanese Patent Kokai NO. 63-120848 discloses such a fuel injection apparatus which achieves this pressure regulation with the use of a pressure regulator provided in the fuel supply passage for varying the amount of excess fuel returned through a return passage to the fuel tank. While the fuel passes the return passage, it is heated to increase the temperature of the fuel stored in the fuel tank. Since the fuel pump is designed to have a sufficient capacity, a great amount of excess fuel will be returned through the return passage so as to produce a great fuel temperature increase which may be a cause of vapor lock.